Alstrostines in Rubiaceae: Alstrostine A from Chassalia curviflora var. ophioxyloides and a novel derivative,rudgeifoline from Rudgea cornifolia

Monoterpenoid indole alkaloids have frequently been isolated from the species-rich Psychotria alliance (Rubiaceae), a complex group including several tribes and genera. In our aim of understanding the chemical diversification within this remarkably heterogeneous group, members of two genera of the tribe Palicoureeae have been studied. Alstrostine A was isolated from Chassalia curviflora var. ophioxyloides, and a novel derivative, rudgeifoline from Rudgea cornifolia, respectively. Alstrostines, an unusual class of alkaloids comprising one tryptamine and two iridoid units, have recently been discovered in Alstonia rostrata (Apocynaceae). The presence of alstrostines in two rubiaceous species is remarkable but not unexpected as both families share similar biosynthetic pathways and are capable of synthesizing related alkaloids.     

Alpneumines A–H,new anti-melanogenic indole alkaloids from Alstonia pneumatophora

Eight new indole alkaloids, alpneumines A–H (1–8) were isolated from the Malaysian Alstonia pneumatophora (Apocynaceae) and their structures were determined by MS and 2D NMR spectroscopic methods. Alpneumines E and G (5 and 7), vincamine, and apovincamine showed anti-melanogenesis in B16 mouse melanoma cells.     

Alstiphyllanines E–H,picraline and ajmaline-type alkaloids from Alstonia macrophylla inhibiting sodium glucose cotransporter

Three new picraline-type alkaloids, alstiphyllanines E–G (1–3) and a new ajmaline-type alkaloid, alstiphyllanine H (4) were isolated from the leaves of Alstonia macrophylla together with 16 related alkaloids (5–20). Structures and stereochemistry of 1–4 were fully elucidated and characterized by 2D NMR analysis. Alstiphyllanines E and F (1 and 2) showed moderate Na⁺-glucose cotransporter (SGLT1 and SGLT2) inhibitory activity. A series of a hydroxy substituted derivatives 21–28 at C-17 of the picraline-type alkaloids have been derived as having potent SGLT inhibitory activity. 10-Methoxy-N(1)-methylburnamine-17-O-veratrate (6) exhibited potent inhibitory activity, suggesting that the presence of an ester side chain at C-17 may be important to show SGLT inhibitory activity. Structure activity relationship of alstiphyllanines on inhibitory activity of SGLT was discussed.     

Taxonomic significance and antitumor activity of alkaloids from Clausena lansium Lour. Skeels (Rutaceae)

Phytochemical analysis of isolates from the aerial parts of Clausena lansium Lour. Skeels (Rutaceae) led to the identification of 14 alkaloids, including two indole alkaloids (1 and 2), one quinoline alkaloid (3), two pyridine alkaloids (4 and 5), four carbazole alkaloids (6–9) and five amides alkaloids (10–14). The phytochemical structures of the alkaloids were established by means of NMR and MS spectral analyses. Compounds (4, 5, 14) were three new natural products, while 1–3 and 10 were firstly reported from the genus Clausena and 8 and 9 were isolated from this species for the first time. The chemotaxonomic significance of these isolated alkaloids has also been discussed. All the isolated alkaloids were tested for their cytotoxic activity against Hela cancer cell line. Among them, four carbazole alkaloids 6–9 exhibited weak cytotoxicity with IC₅₀ values ranging from 69.31 to 138.32 μM.     

Chemical constituents of Gardneria ovata wall

A phytochemical investigation on the aerial parts of Gardneria ovata Wall resulted in the isolation and identification of 14 compounds, including three gardneria glycoalkaloids (1–2 and 6), seven gardneria alkaloids (3–5 and 7–10), and four oxindole alkaloids (11–14). The structure of compound 1 was elucidated by means of spectroscopic analysis, including HRESIMS together with 1D and 2D NMR experiments. Compounds 1–2 and 11–14 are the first time reported from of G. ovate, while the compounds 3–4, 6, and 8 are also the characteristic secondary metabolites of the title plant. The chemotaxonomic significance and distribution of these monoterpenoid indole alkaloids in Gardneria genus are discussed.     

Alkaloids of Toddalia asiatica (Rutaceae)

Phytochemical investigation of the alkaloidal extract of the roots of Toddalia asiatica led to the isolation of a new seco-benzophenanthridine alkaloid (1) and twelve known alkaloids (2–13). The new structure was elucidated by means of spectroscopic analysis, and the known alkaloids were identified by comparison with the literature. Among these alkaloids, 1 and 5–7 were reported from the genus Toddalia for the first time. The distribution of the isolated alkaloids at genus/family level was presented via network analysis and their chemotaxonomic significance was also discussed.     

Isoquinoline alkaloids isolated from three Guatteria species

The chemical investigation of the aerial parts of Guatteria ferruginea collected in the National Park of Serra dos Órgãos, Teresópolis, Brazil and of Guatteria latifolia and Guatteria sellowiana collected in the National Park of Itatiaia, Itatiaia, Brazil resulted in the isolation and identification of six isoquinoline alkaloids, two aporphine alkaloids 3-hydroxy-nornuciferine (1), nornuciferine (2) and four oxoaporphine alkaloids lysicamine (3), isomoschatoline (4), liriodenine (5) and O-methylmoschatoline (6). The isoquinoline alkaloids were found in the species G. ferruginea, G. latifolia and G. sellowiana for the first time and they support the taxonomic position within the genus Guatteria. Isoquinoline alkaloids (5–6) can be considered chemotaxonomic markers of the subfamily Annonoideae.     

Alcaloïdes d'Alstonia vitiensis var. Novo ebudica monachino

Five alkaloids have been isolated from Alstonia vitiensis: pleïocarpamine, vincorine, cabucraline, alstovine (11-methoxycompactinervine) and quaternoxine; the latter two are new alkaloids.     

Alcaloïdes d'Alstonia quaternata

Eleven alkaloids have been isolated from Alstonia quaternata. Three of them, namely 11-methoxy-epi-3α-yohimbine, 10,11-dimethoxy-picrinine designated quaternine, and 19,20-epoxy-N_(a)-methyl, desacetyl, desformo, 2βH-dihydroakuammiline designated quaternoxine, are new alkaloids.     

Alkaloids of Alstonia lanceolifera

Four new indole alkaloids, 10-methoxydeplancheine, 10,11-dimethoxy-1-methyl-deacetyl picraline benzoate, 10,11-dimethoxy-1-methyl-deacetyl picraline 3′,4′,5′-trimethoxybenzoate and 10,11-dimethoxy-1-methyl-deacetyl picraline were isolated from the leaves of Alstonia lanceolifera.     

Further alkaloids of Alstonia muelleriana

Five further alkaloids, des-N′_a-methylanhydromacralstonine, quebrachidine, vinervinine, pleiocarpamine, and 2,7-dihydropleiocarpamine, have been isolated from Alstonia muelleriana bark. Phytochemical problems in the genus Alstonia are considered, especially with reference to the ‘macroline-derived’ indole and bis-indole alkaloids.     

Alkaloids of the stem bark of Alstonia lanceolifera

Nine indole alkaloids were identified from the stem bark of Alstonia lanceolifera: (?)-lochnericine, 10,11-dimethoxy 1-methyldeacetylpicraline 3′,4′,5′-trimethoxybenzoate, 10,11-dimethoxy-1-methylpicraline, akuammiline, picraline, 10-methoxy-nor-C-fluorocurarine, 11-methoxyakuatiammicine, 10-methoxycompactinervine and 11-methoxycompactinervine.     

Alkaloids from the stem bark of Strychnos icaja

A comprehensive phytochemical study of the stem bark of Strychnos icaja was done for the first time and led to the isolation of two new monoindole alkaloids 15-hydroxyvomicine (1) and 12-methoxyicajine (2) along with 13 known alkaloids: the monoindoles N-methyl-sec-iso-pseudostrychnine (3), vomicine (4), icajine (5), 19,20-α-epoxy-12-methoxyicajine (6), 19,20-α-epoxy-12,15-dihydroxy-11-methoxyicajine (7), 19,20-α-epoxy-15-hydroxynovacine (8), 15-hydroxyicajine (9), 12-hydroxystrychnine (10), strychnine (11) and the tertiary bisindoles sungucine (12), isosungucine (13), strychnogucine C (14) and bisnordihydrotoxiferine (15). Apart from 10 and 11, the other alkaloids were isolated for the first time from the stem bark of this plant. The hemisynthetic derivative, N_b-chloromethosungucine (16) and the previously reported synthetic compound 3 were isolated from a natural source for the first time. Fractions and some isolated compounds were tested against the chloroquine-sensitive 3D7 strain of Plasmodium falciparum. The bisindole alkaloids were most active with IC₅₀ ranging from 0.72 to 3.41 μg/ml whilst the monomers 1 and 3 were slightly active (IC₅₀ 39.92 and 40.27 μg/ml respectively) and 6 inactive. The structures of the compounds were determined based on the analysis of their spectral data. The full ¹H and ¹³C NMR data of compounds 3, 6 and 7 are also reported in the present work for the first time.     

Pyrrole alkaloids from the fruits of Morus alba

Phytochemical investigation of the fruits of Morus alba afforded seventeen pyrrole alkaloids including five new compounds. The structures of five new pyrrole alkaloids, named morroles B–F (4, 5, 7, 16 and 17), were determined on the basis of spectroscopic interpretations. 4-[Formyl-5-(hydroxymethyl)-1H-pyrrol-1-yl]butanoate (2) was synthesized by chemical reaction but first isolated from nature. Among isolated compounds, compounds 6 and 14 significantly inhibited pancreatic lipase activity.     

Two tetrahydroisoquinoline alkaloids from the fruit of Averrhoa carambola

The fruit of Averrhoa carambola, commonly known as star fruit or carambola, is popular in Southeast Asia and China. Two new tetrahydroisoquinoline alkaloids, (1R*,3S*)-1-(5-hydroxymethylfuran-2-yl)-3-carboxy-6-hydroxy-8-methoxyl-1,2,3,4-tetrahydroisoquinoline (1) and (1S*,3S*)-1-methyl-3-carboxy-6-hydroxy-8-methyoxyl-1,2,3,4-tetrahydroisoquinoline (2), were isolated from the fruit, along with vanillic acid (3), ferulic acid (4), 8,9,10-trihydroxythymol (5), and arjunolic acid (6). Their structures were elucidated by spectroscopic method. Compounds 1, 2, and 5 showed weak ferric reducing antioxidant potency (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity.     

Alkaloids of Alstonia plumosa

Nineteen indole alkaloids have been isolated from the root and stem barks of Alstonia plumosa, from New Caledonia. Twelve of them were known compou     

Unusual C19-diterpenoid alkaloids from Aconitum vilmorinianum var. patentipilum

Three new C₁₉-diterpenoid alkaloids vilmotenitines A-C (1-3), together with seven known ones, vilmorine D (4), talatizidine (5), isotalatizidine (6), vilmorrianine B (7), vilmorrianine D (8), talatizamine (9), 8-deacetyl-yunaconitine (10), were isolated from Aconitum vilmorinianum var. patentipilum. Vilmotenitines A (1) and B (2) are the second natural occurrences of C₁₉-diterpenoid alkaloids with a unique rearranged six-membered B ring formed by the C₍₈₎–C₍₁₀₎ linkage.     

Alkaloids of Alstonia lanceolata

Thirteen alkaloids were isolated from the stem bark of Alstonia lanceolata. They were lochnericine, gentianine, 10,11-dimethoxy-1-methyl-deacetylpi     

Alcaloïdes des feuilles et écorces de tronc d'Alstonia odontophora

Six known indole alkaloids were isolated from the leaves and stem bark of Alstonia odontophora: vincamajine, 11-methoxy- akuammicine, quebrachidine, pleiocarpamine, antirhine, pleiocorine and pleiocraline, along with the novel bisindole, N (I′)-demethylpleiocorine.     

Six new norditerpenoid alkaloids from Delphinium elatum

Six new C₁₉-norditerpenoid alkaloids, N-formyl-4,19-secopacinine (1), iminoisodelpheline (2), iminodelpheline (3), iminopaciline (4), 6-dehydroeladine (5), and elapacidine (6) were isolated from Delphinium elatum cv. Pacific Giant.